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ext4: Add sanity check to make_indexed_dir

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Make sure the rec_len field in the '..' entry is sane, lest we overrun
the directory block and cause a kernel oops on a purposefully
corrupted filesystem.

Thanks to Sami Liedes for reporting this bug.

http://bugzilla.kernel.org/show_bug.cgi?id=12430

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
This commit is contained in:
Theodore Ts'o 2009-01-16 11:13:40 -05:00
parent 06a279d636
commit e6b8bc09ba
1 changed files with 15 additions and 6 deletions
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21
fs/ext4/namei.c
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@ -1368,7 +1368,7 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
struct fake_dirent *fde;
blocksize = dir->i_sb->s_blocksize;
dxtrace(printk(KERN_DEBUG "Creating index\n"));
dxtrace(printk(KERN_DEBUG "Creating index: inode %lu\n", dir->i_ino));
retval = ext4_journal_get_write_access(handle, bh);
if (retval) {
ext4_std_error(dir->i_sb, retval);
@ -1377,6 +1377,20 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
}
root = (struct dx_root *) bh->b_data;
/* The 0th block becomes the root, move the dirents out */
fde = &root->dotdot;
de = (struct ext4_dir_entry_2 *)((char *)fde +
ext4_rec_len_from_disk(fde->rec_len));
if ((char *) de >= (((char *) root) + blocksize)) {
ext4_error(dir->i_sb, __func__,
"invalid rec_len for '..' in inode %lu",
dir->i_ino);
brelse(bh);
return -EIO;
}
len = ((char *) root) + blocksize - (char *) de;
/* Allocate new block for the 0th block's dirents */
bh2 = ext4_append(handle, dir, &block, &retval);
if (!(bh2)) {
brelse(bh);
@ -1385,11 +1399,6 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
EXT4_I(dir)->i_flags |= EXT4_INDEX_FL;
data1 = bh2->b_data;
/* The 0th block becomes the root, move the dirents out */
fde = &root->dotdot;
de = (struct ext4_dir_entry_2 *)((char *)fde +
ext4_rec_len_from_disk(fde->rec_len));
len = ((char *) root) + blocksize - (char *) de;
memcpy (data1, de, len);
de = (struct ext4_dir_entry_2 *) data1;
top = data1 + len;